<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>设置上边框的宽度</title>
</head>

<style>
    .demo {
	width: 200px;
	height: 200px;
	padding: 20px;
	background-image: url(test.jpg);
	background-repeat: no-repeat;
	background-size: 50% 50%;
}
    </style>
    </head>
    <p>这是一个段落</p>

</html>